1. Field of the Invention
The present invention relates to an information playback apparatus and an information playback method.
2. Description of the Related Art
As is well known, currently, there is an optical disk which is called digital versatile disk (DVD) in which digital information can be played back by using a converging light. As the existing DVD standards, there are a DVD-ROM standard which is a read-only type, a DVD-R standard which is a write-once type, a DVD-RW standard which is a rewritable (about 1000 times) type, and a DVD-RAM standard which is a rewritable (10000 times or more) type. In any standard, there is provided a format standard for providing a data structure of image information [which is an video object the general term for video data, sub-picture data, and voice data] itself recorded on an optical disk (information storage medium), and a data structure of the management data for managing the image information.
The existing DVD video standard which is a read-only type corresponds to multiple languages simultaneously, and is made to be in a format in which not only multi-scene expression such as multi-angle/multi-story or the like is possible, but also a menu screen is satisfactory and it is easy for a user to directly access to a scene which the user wishes to see, and the like which can provide image contents that are easy for a user to use (for example, refer to the specification of U.S. Pat. No. 5,636,200 and the specification of Japanese Patent No. 2,677,775).
As described above, although the existing DVD video standard which is a read-only type is made to be in a format in which image contents that are easy for a user to use can be provided, the improvement with respect to the standard has been required in order to make a user to even more easily use it, and to enrich the contents expressive power with respect to the user.
Further, in order to provide contents that are easy for a user to use, there is the problem that authoring (preparation and editing of a program to be recorded on a DVD video disk) is made complicated.
Points in which the contents expressive power with respect to a user is insufficient, points which are difficult for the user to use, or points in which authoring is made complicated in order to provide contents that are easy for a user to use in the existing DVD video standard will be concretely enumerated.
[1] It is difficult for a user to use. Or, in order to prepare contents that are easy for a user to use, authoring is complicated.
(A) A defective point with respect to a playback start position when the playback is interrupted during a playback of a title, and carrying out some other processings, and thereafter, the process returns to the playback of the title.                (A1) When an image is interrupted to play back, and it is made to return to the playback after switching to display a menu or an image, it is impossible to play back the image from the former position interrupted.        
In many cases, after the playback is interrupted during a playback of a specific image title, and the screen is switched to a menu screen, and bonus contents are played back up to the middle or the end thereof, and thereafter, when an attempt is made to play back the image title which has been interrupted during the playback, the contents prepared in accordance with a conventional DVD standard cannot be played back from the other positions except for the top position of the image title. This is because the resume information (playback-interruption positional information) of the specific image title is rewritten to the positional information of the bonus contents at the stage of starting to play back the bonus contents. In order to make the contents be contents which can be stated to play back from a position at which the image title has been interrupted previously after the bonus contents are played back up to the middle or the end thereof, complicated authoring is required.                (A2) In a case of a game or the like, when an attempt is made to play the game again after interrupting a playback thereof, it is impossible to start the playback from a convenient position.        
When a “game” (for example, a role playing game) is carried out as a specific title in place of the above-described image, at the time of restarting the game after returning to a menu screen, there is a request to make an attempt to start the game from, not the interrupted position, but a pause of a chapter of the game from the side of a contents provider. However, it is impossible to cope with the request in the existing DVD video standards.
(B) There is a point which is difficult to use with respect to display-oriented language setting.                (B1) It is impossible to change a menu description language code by a command which can be designated in the contents, and the authoring is complicated.        
In the existing DVD video, a menu description language code (M_LCD) is set in SPRM(0) (the system parameter of No. 0: 16 bits), and the value thereof is stored in a memory unit 122 of an information playback apparatus of FIG. 48. In the existing DVD video standard, there is no command for changing the value of SPRM(0) in a command list which can be set in the contents, and it is possible to change the value of SPRM(0) by only a user instruction under a special condition. To describe concretely, the value of SPRM(0) can be changed by using a user operational function called Menu_Language_Select( ) among the user functions installed in the information playback apparatus. However, the user operation called Menu_Language_Select( ) has a restriction in which it is possible to set only while the information playback apparatus is stopped to operate. This user operation is set by using a remote controller while a single-purpose screen is being displayed.
In this way, because the value of SPRM(0) cannot be changed by a command which can be set in the contents, it is necessary to prepare a screen on which a menu description language code is respectively selected for a plurality of menu description language codes in the contents (in particular, VOB data on the menu information) so as to cope with a case even if the value of SPRM(0) is set to any value, so that the authoring operation at the time of preparing the contents has been extremely troublesome.                (B2) The risk that the information of the menu description language code set by a user is deleted is brought about.        
For example, if a command by which the value of SPRM(0) can be changed in the contents is newly added in order to solve the problem of (B1), there is a risk that the value of SPRM(0) is automatically changed by playing back the contents even if the user sets a specific menu description language code (for example, Japanese to SPRM(0)). When the menu description language code is automatically changed by the command, not only the user is dissatisfied, but also the problem that the need for resetting a menu description language code by the user is brought about, which brings about the problem increasing the burden imposed on the user.
[2] There is a part at which the contents expressive power with respect to a user is insufficient.
(C) A defective point relating to a seamless playback with respect to a still picture content.                (C1) A seamless connection between a movie content and a still picture content is impossible in existing DVD video contents.        
In an existing DVD video, a seamless playback of a movie content is guaranteed, and it is possible to seamlessly connect and play back over different VOBs (or different titles) (without the screen of the movie content being disconnected). In contrast thereto, a seamless playback is not guaranteed, for example, when a still picture content displayed by a slide show (one method of display for still picture contents in which still picture contents to be displayed are automatically switched) is switched to a movie content, and there are cases where the image or the voice stands still depending on an information playback apparatus. The reason for that a seamless connection is not guaranteed at a point in time of switching from a still picture content to a movie content in the existing DVD video contents is that:
i) in an extended system target decoder (E-STD) model in which a seamless playback is guaranteed, an access unit is defined in a movie content object, and values of system time clock (STC: clock values to be references) set in a separation unit 103, a video decoder unit 111, a sub-picture decoder unit 112, and an audio decoder unit 114 which are shown in FIG. 48 are switched at a position of the boundary of the access unit. In contrast thereto, in the existing DVD, an access unit cannot be defined for a still picture content.
Namely, a movie content continues to continuously output pictures always in units of fields. In contrast thereto, for example, a still picture content displayed by a slide show outputs pictures intermittently. As a data structure in a still picture content object, a sequence end code (sequence_end_code) is disposed immediately after an Intra picture (I picture) configuring one still picture content in accordance with the standard of MPEG2 (Moving Picture Experts Group 2), and in the video decoder unit 111, the decoding is stopped until the next picture comes when the sequence end code is sensed. Accordingly, in the conventional DVD video, an access unit as that in a case of a movie content cannot be set during a period in timings when a still picture content intermittently outputs.
ii) In the conventional DVD video, switching among common parities has been allowed as the timing of switching among still picture contents. Namely, after a previous still picture content is completed at the top field (or the bottom field), the next still picture content is allowed to start from the top field (or the bottom field). Accordingly, when it is switched from a still picture content to a movie content in the middle of a frame, a seamless connection cannot be carried out, and there is the risk that the screen is disturbed at the switching point.                (C2) A multi-angle playback in which still picture contents are combined, and a multi-angle playback between a movie content and a still picture content are impossible.        
In the existing DVD video, a multi-angle playback in which slide shows of still picture contents are combined, and a multi-angle playback in which a slide show of still picture contents and a movie content are combined are difficult. When contents corresponding to a multi-angle playback are compulsorily prepared, a seamless playback with respect to still picture contents is not guaranteed. Therefore, there are cases where still picture contents which have been at multi-angles cannot be continuously played back (a still picture content is stopped due to the still picture contents being not continuously switched), or the screen is stopped during the playback due to a screen of a multi-scene and a screen of a one sequential scene being not switched smoothly at a switching point therebetween. This is because, although an interleaved unit (ILVU) which carries out arrangement to disperse for at each angle in an interleaved block is defined in a movie content, the definition of an ILVU with respect to a still picture content is not made clear in the existing DVD video. Further, in a still picture content, a period up to switching a screen is long (because a same still picture content is continued to play back for a long time), and there is no mechanism under the existing circumstances in which a corresponding still picture content can be immediately displayed immediately after switching the angle. Moreover, as described in (C1), when the sequence end code disposed directly after the I picture corresponding to the still picture content is detected, decoding processing of the video decoder unit 111 is temporarily stopped until the next I picture comes. Therefore, in the existing DVD video standard, disposition of a sequence end code in video data in cells configuring an interleaved block is prohibited.
(D) A seamless playback at a place of VOB into which a command in a cell unit is included is not guaranteed.
In the existing standard definition (SD) DVD video, it is possible to designate a command in a cell unit in a program chain (PGC). The command information is recorded within a cell command area 513 in a program chain information (PGCI) which is an area on which management information of the PGC has been recorded in the same way as in FIG. 35. Because the cell command is executed at a point in time when a playback of the cell in which the cell command 513 is set is completed, a playback of the following cell can be temporarily interrupted. Therefore, in the existing SD DVD video, a seamless playback between cells is not guaranteed at the time of playing back VOB including the cell command 513.
(E) A defective point with respect to highlighted information.                (E1) A gap between the displaying periods (setting periods) occurs between highlighted information and a sub-picture.        
A menu of highlighted information is displayed at the time of playing back a video title image, and contents can be prepared so as to allow a user to interactively operate it. In this case, because it is necessary to switch the highlighted information in accordance with the contents of the video title image in process of playback, or to change the contents, the accuracies in a displaying period of the highlighted information and a valid executable period are important. In the conventional SD DVD video contents, buttons displayed on the screen are composed of a combination of two types of separate streams, i.e., a sub-picture stream which provides pictures of the buttons and a video stream including highlighted information necessary for executing a command designated by a button.
The valid executable period of highlighted information is provided in accordance with time information (PTM: Presentation Time) of the start and the end, and is completely coincident with the displaying period of a sub-picture mainly used for a caption or the like, and there is the problem that, when the sub-picture ends, a menu selection as well ends. Therefore, when a contents manufacturer makes an attempt to manufacture contents in which a caption and a menu are simultaneously combined, there is a limitation in preparing the contents, such as it is necessary to cause a user to execute a menu selection within the valid (displaying) period of a sub-picture, and the like. Thus, the contents manufacturer cannot prepare contents as he/she has imagined, the degree of freedom is limited, and a limitation to contents to be provided to a user is unavoidable.                (E2) Pictures of selection items in the menu are not multicolored.        
Because a color scheme can be expressed in only 16 colors in the existing SD DVD video contents, the degree of appeal to a user is low, and multicolored color-expression is impossible.                (E3) An area on which highlighted information is designated cannot be set to be a shape except for a rectangle.        
In the existing SD DVD video contents, shapes except for a rectangle cannot be set as an area on which highlighted information is designated, and for example, contents full of variety such as, for example, a triangle and a star shape cannot be prepared.                (E4) A same button cannot be set with respect to a plurality of areas separated from one another on the screen.        
In the existing SD DVD video contents, a same button can be set only within areas in one place together with one another.
As compared therewith, on a screen of a PC or a screen of a homepage on Internet, it is easy to make a same URL link with a plurality of areas in the screen, and the existing SD DVD video contents have been not as good as a screen of a PC or a screen of a homepage on Internet.
(F) There is the problem that background music skips at the time of switching a menu screen.
In the existing SD DVD video contents, voice information at the time of displaying a menu screen (background music) is made to accompany with each menu. Accordingly, voice information is changed every time of changing the menu screen.
The request of a contents provider to want to play back background music continuously without being disconnected even if a menu is switched cannot be satisfied by the existing SD DVD video contents. Moreover, for example, a request of a contents provider to want to prepare contents cannot be satisfied such that:
i] background music is played back continuously without disconnecting the sound at the time of switching a menu, and a range within which the background music is repeatedly played back is changed in accordance with a menu screen (for example, while “top menu screen” is being displayed, “the first verse of the music” is repeatedly played back, and in contrast thereto, while “specific menu screen A” is being displayed, “the first verse to the third verse of the music” are repeatedly played back, and while “specific menu screen B” is being displayed, only “the most elegant part further in the first verse of the music” is repeatedly played back; or
ii] without discontinuously changing background music at the same time of switching the menu screen, the background music corresponding to a menu screen continuously switched is started immediately after the background music corresponding to a menu screen before switching is completed to the end, and thereafter, the background music corresponding to the menu screen after being switched is repeatedly played back.
Further, at the present time, a so-called HD (high definition)-DVD in which it is possible to record information of 4 to 5 times of a DVD by carrying out recording and playing back information by using, for example, a blue laser beam whose wavelength is about 405 nm has been developed, and an HD-DVD video standard for that has been also established.
In the HD-DVD video standard, the main image information is at HD (high definition), and in contrast thereto, there are two types of HD and SD (standard definition) as sub-picture information. Therefore, at the time of displaying an image such that sub-picture information is superimposed onto main image information, the need for matching the definitions between the main image and the sub-picture is brought about.
In Jpn. Pat. Appln. KOKAI Publication No. 2001-320673, there is disclosed a configuration in which mass storage multimedia information including a main image, a sub-picture, voice data, and the like is decoded and played back by a simple hardware configuration. However, in the specification of U.S. Pat. No. 5,636,200, there is no description on the fact that the definitions between the main image and the sub-picture must are matched.